Carbon dioxide presents several environmental problems in modern society. Carbon dioxide is a colorless, odorless component of the earth's atmosphere that is transparent to visible light, but opaque to long wave infrared radiation. Carbon dioxide is an important component of the earth's atmosphere because it allows visible light to pass through the atmosphere while trapping part of the long wave infrared radiation as it reflects and radiates from the surface of the earth in the form of heat. This heat capturing quality of the earth's atmosphere maintains the delicate balance that safely sustains life on earth within the frigid voids of space. Unfortunately, modern processes emit tremendous quantities of carbon dioxide into the atmosphere, which will likely lead to a continuous terrestrial warming. It is feared that such warming will cause a heat and radiation imbalance similar to the principal employed to heat greenhouses, thereby altering the ecosystem. Therefore, the need exists to reduce the amount of carbon dioxide that enters the atmosphere.
Two basic alternatives exist to reduce the amount of carbon dioxide entering the atmosphere. The first alternative involves reducing the amount of carbon dioxide that is emitted from industrial processes. The second alternative involves recycling the carbon dioxide within the earth's atmosphere.
Recycling carbon dioxide will greatly reduce the potential for terrestrial warming, and if recycled properly, additional environmental problems may be substantially reduced. One such problem is the amount of water used to irrigate crops in the areas where water is in short supply, such as in the western United States. A significant amount of money has been spent building an infrastructure to store water in dams, retrieve water from underground aquifers and deliver water from where it is stored to the crops via aqueducts. The current water management system in the United States has caused significant environmental damage. Many major rivers, such as the Colorado River, have significantly reduced stream flows because of the amount of water that is used from these rivers to irrigate crops. Reduced stream flows significantly damage fish runs and drain valuable wet lands, destroying valuable and irreplaceable ecosystems. Also, water from underground aquifers is being drained faster than it can be replenished, causing the water level in some aquifers to drop as much as thirty feet in one year. As these underground aquifers continue to be drained, the pumping height increases, causing a greater expenditure of energy to pump the same volume of water. Additionally, soil salinization occurs after extensive irrigation because salts build up in the ground water and at the surface. Certain parts of the San Joaquin Valley in California have salt levels that are toxic to plants because of over irrigation.
Another significant problem that may be substantially reduced by recycling carbon dioxide is the use of fertilizers and pesticides to enhance agricultural yields. Although fertilizers enhance the growth of many crops, they also damage the soil and leach into the ground water, contaminating the surrounding environment. Similarly, pesticides damage the soil and are a health hazard to small children who eat foods which have been treated with pesticides. Pesticides and fertilizers also are costly to buy and distribute onto the crops. Therefore, the need exists to reduce carbon dioxide pollution to prevent global warming, while also reducing the amount of water irrigation and chemical treatment of agricultural crops.
The environmental problems of carbon dioxide pollution, irrigation of crops and chemical treatment of crops can be addressed by recycling carbon dioxide for absorption into plants. It is well known that plants require carbon dioxide gas to "breathe." During the process of photosynthesis, plants exchange carbon dioxide gas, oxygen and water through their stomatal openings when they are exposed to sunlight. This process is known as transpiration. As plants transpire, carbon dioxide gas enters the plant and water evaporates through the stomatal openings. It is well known that carbon dioxide gas is a limiting factor in plant growth, and that exposing plants to greater ambient carbon dioxide gas concentrations will produce greater plant growth. Such exposure to above normal ambient carbon dioxide concentrations will also cause the stomata to restrict, thereby significantly reducing the amount of water lost during transpiration.
One advantage of exposing crops to carbon dioxide is that a significant amount of carbon dioxide will be absorbed by the crops instead of entering the atmosphere. Another advantage of exposing crops to carbon dioxide is a significant reduction in the amount of water required to grow crops. As discussed above, the introduction of carbon dioxide enhances the efficiency of the transpiration process which reduces the amount of water the plants lose through their stomata. In addition, the total number of plants can be reduced because each individual plant will produce a higher yield, thereby reducing the number of plants required to grow the same volume. This will not only reduce the burden that irrigating crops places on rivers, lakes and underground aquifers, but it will also reduce the increasing cost of storing and delivering the water.
Another advantage of exposing crops to carbon dioxide is a significant reduction in the amount of fertilizer required to grow high yield crops. Instead of using chemical fertilizers to enhance growth, carbon dioxide will provide sufficient growth rates to produce the required yield. This will reduce the contamination caused by fertilizers and the associated health hazards that fertilizers have on small children. Therefore, a tremendous need exists to recycle carbon dioxide gas by large-scale exposure for absorption into plants in order to simultaneously reduce carbon dioxide pollution, irrigation requirements and the use of fertilizers.
Yet another advantage of exposing crops to carbon dioxide is the use of carbon dioxide as a substitute for environmentally damaging pesticides. Pulses of carbon dioxide concentrations can be used to flood the crops with carbon dioxide, thereby displacing the oxygen next to the plants and suffocating unwanted insects. Alternatively, low concentrations of safe pesticides may be added to a carbon dioxide stream being delivered to the crops.
Current methods and apparatuses, however, are not effective or economically viable. Enhancing plant growth using carbon dioxide is presently being employed in greenhouses. Although greenhouses are advantageous in that they may use natural sunlight and the delivery of the carbon dioxide is easily controlled, it is impractical to encapsulate entire crops with a greenhouse in order to deliver and keep the carbon dioxide in close association with the biomass. In other cases, carbon dioxide has been drawn from the depths of coal mines, and pumped into greenhouses. In addition to the problems associated with greenhouses, oxygen-rich ambient air enters the coal mines as the carbon dioxide is withdrawn, causing oxidation of pyrites in the mines, which leads to acid mine drainage.
Another current solution of distributing carbon dioxide to plants uses a fixed overhead gas irrigation system suspended from the roof of a greenhouse. Such fixed systems are not practically applied to outdoor application in large fields because they would obstruct tractors, harvesters or other farm equipment necessary to grow and harvest crops and carbon dioxide delivery to the plants would be disrupted by wind currents.
Free-air CO.sub.2 enrichment systems have been developed in which carbon dioxide is distributed to plants using a system of horizontal and vertical pipes with discharge jets through which carbon dioxide may pass. The free-air CO.sub.2 enrichment systems, however, do not address the problem of deploying tractors and other farm equipment in fields having such piping. Additionally, such systems are generally inefficient because a great deal of carbon dioxide is lost to the atmosphere.
Attempts have also been made to irrigate plants with carbonated water. The concept is that the carbonated water would release carbon dioxide into the plants as the carbon dioxide escapes from the water. These attempts, however, have proven deficient because such carbon dioxide has a low density and merely rises in the surrounding ambient air.
Experiments have been employed utilizing carbon dioxide by bubbling the carbon dioxide through algae ponds to allow aquatic vegetation to consume the carbon dioxide. Although certain algae consume large amounts of carbon dioxide, this method may be impractical because thousands of square miles of water is required to absorb even a small fraction of the carbon dioxide that is produced and delivery of the carbon dioxide to remote locations such as in the ocean may be very costly. Additionally, the effects of growing such large quantities of algae on the environment have not yet been ascertained, and it is possible that such large quantities of algae may have negative environmental ramifications.
A method and means for enhancing plant growth under field conditions is disclosed in the present inventor's U.S. Pat. No. 5,300,226 for a WASTE HANDLING METHOD, the disclosure of which is herein incorporated by reference. This patent discloses a plurality of trenches which may be located above a strip mine for growing plants, but it does not provide a particularly effective method for economically increasing the density of the carbon dioxide to limit loss of carbon dioxide to the atmosphere before it can be absorbed by the plants.
The current methods and apparatuses for delivering carbon dioxide to plants fail to provide an effective system for enhancing plant growth. One problem common to such systems is that they do not provide a method or system that addresses the transmission, storage, and distribution problems associated with delivering large volumes of carbon dioxide to large agricultural and silvicultural uses in a manner that will prevent the carbon dioxide from entering the atmosphere before it is absorbed. Therefore, there is presently a significant need to provide a method that economically and effectively distributes large quantities of carbon dioxide to plants in order to reduce the amount of carbon dioxide in the atmosphere and to use waste carbon dioxide for beneficial purposes, such as to reduce the amount of water and fertilizer used to grow crops.
In addition to recycling carbon dioxide for absorption in plants, carbon dioxide may be used to reduce the potential for fires in abandoned mines. In order to avoid such fires, mine operators currently install elaborate and expensive fire prevention systems when a mine is shut down. Recycling carbon dioxide into mines, however, will displace the oxygen necessary for combustion. Thus, recycling carbon dioxide into a mine after it is shut down will significantly reduce mine fires at a fraction of the cost of current systems.